Effect of Azolla meal-based diet on growth performance, haematological profile and proximate composition of common carp (Cyprinus carpio) fry

Optimising the cost of nutrients in fish diets is crucial for aquaculture production, as feed accounts for 50% of operational expenses in intensive aquaculture. The rising demand for mustard oil cake (MOC), a commonly used feed ingredient in Indian aquaculture, has led to a significant increase in its price due to its diverse applications. Azolla (Azolla pinnata), a free-floating freshwater plant, has attracted researchers in fish feed formulation due to its rich nutrient profile. The present study was conducted to evaluate the effects of replacement of MOC with Azolla meal in the diet of common carp (Cyprinus carpio) fry. Pelleted feed was formulated with Azolla meal replacing MOC at levels of 0, 10, 20, 30 and 40% and fed to fish. Growth performance, feed conversion ratio (FCR), haematological parameters and proximate composition in fish carcass were assessed after 90 days of experimental feeding. Simultaneously, a control feed without supplementing of Azolla meal was also prepared. Fish were fed daily with the experimental diets at 8, 6 and 4% of their body weight during the first, second and third months respectively, in the morning hours (10:00 hrs). Principal component analysis (PCA) was performed to assess the effect of formulated diets on fish carcasses composition and haematological parameters. The results showed that replacing 30% of MOC with Azolla meal in the diet, led to significantly (p≤0.05) higher specific growth rate (SGR) and percentage weight gain and significantly (p≤0.05) lower feed conversion ratio (FCR) at this concentration. Fish survival rate ranged from 80.00 to 93.33% among different treatments. Further, significant (p≤0.05) differences were observed in both haematological parameters of fish and the proximate composition of fish carcass. among the different treatments. These findings suggest that MOC can be effectively replaced with 30% Azolla meal in the diet for rearing common carp fry to fingerling stage, without compromising the growth performance.   Keywords: Aquaculture, Feed conversion ratio, Health status, Mustard oil cake, Principal component analysis, Specific growth rate, Survival